[heap] Remove unused CompactionMode flag

src/heap/mark-compact.h

Index: src/heap/mark-compact.h
diff --git a/src/heap/mark-compact.h b/src/heap/mark-compact.h
index 91842bc0da1f47dfbe5be03dd120f9642b913c5c..21b0e4c62fa55f82cfcf28a8134c7fb8257f64c0 100644
--- a/src/heap/mark-compact.h
+++ b/src/heap/mark-compact.h
@@ -431,9 +431,7 @@ class MarkCompactCollector {
   // Performs a global garbage collection.
   void CollectGarbage();
 
-  enum CompactionMode { INCREMENTAL_COMPACTION, NON_INCREMENTAL_COMPACTION };
-
-  bool StartCompaction(CompactionMode mode);
+  bool StartCompaction();
 
   void AbortCompaction();